I've held this e-mail hostage for far too long. As previously declared, Around the Horn has come to employ a staff paleontologist in New Mexico, Ralph E. Chapman, formerly of the Smithsonian, who's generously agreed to answer the show's dino-queries via e-mail. Our very first question read as follows:

Which dinosaur would you draft first in a one-on-one Mortal Kombat Dinosaur Fighting Tournament? Feel free to separate answers by weight classes of your own creation, if that's sensible.

Ralph responded with great force, and for your perusal. Enjoy, friends:

OK, so let’s talk Mortal Kombat.

If you keep it within the dinosaurs, all the meat eaters (known as the theropods) are bipedal. Some of the plant eaters are as well, although many are quadrupedal (walk on 4 legs). Combat between the two types may be odd, so we may want to keep it within bipeds and within quadrupeds and not mix the two types (or maybe not). Combat between a theropod and a quadrupedal dinosaur is called predation.

A quick note. Dinosaurs evolved back and forth between bipedal and quadrupedal a lot. The reason for this is probably because the limb joints in dinosaurs and other archosaurs tend to be more cartilaginous and this means the joints are not as tightly coupled as in many mammals – think of the ball and socket joint of your hip, a real tight fit. So more flexibility is possible through evolutionary processes. The big reason, however, is that reptiles are back-end loaded, meaning the main focus biomechanically for locomotion in dinosaurs is the hip joint and the muscle connection to the tail. Archosaurs tend to have really prominent and muscular hips and the front of their tails. This is why I will sometimes refer to them as the Kardashians of the paleo world; huge back ends (except the dinosaurs are far less hairy and, probably, in most cases far more intelligent).

Our line, the therapsids, which later produced the mammals, actually went through an early process of modifying these muscular connections in the back and became more front-end loaded – the dominant limbs are the front ones – think bulldogs. This is why a dog with paralyzed back legs can get a cart and motor about pretty happily using their front legs. Paralyze the front legs and they tend to be in much worse shape. You can see the result of this evolution by comparing porpoises and ichthyosaurs (swimming reptiles that look very similar to them or, more accurately since they were first, porpoises look like ichthyosaurs). When ichthyosaurs swam, the propulsion came from a sideways movement of the tail; reflecting the slithering you see in lizards and snakes and crocs and even the amphibians and fish that started it. Porpoises move their tails up and down, reflecting the new muscle structure and front-end loading we mammals have.

So, if your front end is not dominant, it makes it easier to become bipedal and the dinosaurs did it many times, and even went in reverse. Bipedality, as we humans have, is a rare state for mammals.

Anyway, back to combat. If you make the assumption that predators are nastier and better armed than herbivores, then you can pretty much ignore the herbivores that are bipedal as they are mostly food. Some are real big, though, which would be a natural defense against the smaller theropods. They would just step on them.

So we are dealing with theropod on theropod combat. Size classes would be important and you can break it down to <10 feet long, 10<x<20 feet long, between 20 and 35ish feet, and the big chaps moving towards 45 feet or more. In all categories where we know them from, the dromaeosaurs would be a great bet for the nastiest and best fighters because they are fast, smart, and have a relatively big old recurved claw –a real weapon – on each foot. It would serve nicely for evisceration (we actually see evidence for this in the original fighting dinosaurs from Mongolia where a Velociraptor is doing this to a Protoceratops but the latter chomped on and broke the front arm of the former and they both died and were buried and preserved). Dromaeosaurs include Velociraptor and Deinonychus, although sometimes they are split into 2 subfamilies of closely related forms. The former you supposedly saw in Jurassic Park but they were a bit larger than real ones we know of that only got to be about 6 feet long at most, but not that tall. The one in the movie would be closer to Deinonychus, which is a larger cousin from North America. So I would say Velociraptor would rule the smallest size class and Deinonychus the 2nd category, as it got to about 12 feet long. Just nasty, though. You want an idea, see the modern flightless bird, the cassowary, that can eviscerate a human with less of a claw. [Ed. note: Watch this BBC documentary on cassowaries right now because they're insane.] Lots of other nasties in these two categories, but there is nothing like good weaponry.

Now let’s go to the real big chaps, pooching into the 40 foot or larger size. Certainly T. rex would be a contender. It just has that huge head and teeth. It seems to come in thinner (we say gracile) form, and a more robust form, but they were sleek animals. To use an NFL analogy, think T.O. for the gracile (except 40 foot long) and Megatron for the robust. SUE at the Field museum would be the latter (my company virtualized SUE for the Field – coordinated a complete 3-D scan of it). Good contenders all, although the robust would mostly win out over the gracile, I suspect. Now there are other really big theropods that are less sleek and more fullback or linebacker like. Acrocanthosaurus from the Early Cretaceous is a big bruiser that at times seemed to go after huge sauropods (brontosaur-like dinos). So LeBron to use the NBA player as a model. But my money would be on Giganotosaurus from Argentina (note NOT Gigantosaurus but Giganotosaurus) which was huge and bulky. So Shaq. Carcharodontosaurus from North Africa, a relative of Giga would also be impressive as would be the largest Allosaurus. No dromaeosaurs got this large that we know of (still hoping).

The fun size range is in the 20-35 foot size range. Here you would get teenage versions of the big chaps, as well as some other wonderful theropods. Allosaurus is mostly found at this size and would have had great weaponry in the teeth, the hands, the legs and the tail. All armament. At the meeting we just got back from, there was a description of a new dinosaur Lythronax, a tyrannosaur, and its name actually means the King of Gore (not Al). There are other tyrannosaurs here as well. But my favorite for this is the very large dromaeosaur Utahraptor, which has a claw about 9 inches long (without the covering sheath) and would have been a hellion. It was described by my buddy Jim Kirkland, the state paleontologist of Utah and was recently also found at a quarry I worked with him early on (my part was trivial). They now have a huge growth series for this one, starting at hatchling size. So, Utahraptor would have the other armament similar to the other species at that size range, plus the special weapon of the recurved claws (hands and feet).

Quick note on the herbivores. Most are just food and are either quick, or in huge numbers. The best potential fighters are, of course, the horned dinosaurs, some stegosaurs, and the tank-ish ankylosaurs, some of the latter with the a big boney ball at the end of its tail. Not the brightest bulbs, though, but I would go with a big anky because there is not much unarmored stuff to hit or bite.

If the theropods and these latter guys are fighting, certainly the ankys would nail the lower legs because, as we know, helmet to helmet is a penalty. Stegos do have the spikes on their tails to be careful of (named the Thagomizer in a Gary Larson Far Side cartoon – Linda and I have the original art for that one – and the term is now used by dinosaur paleontologists). Triceratops and friends would probably only be a last resort kill in the Cretaceous for a tyrannosaur, but would make a good match in Mortal Kombat.

If you included some pre-dinosaur cousins, there is a form called Postosuchus (don’t know why the USPS doesn’t use it as a mascot) which is very croc-like except not flat but more lizard like in general look (not dorso-ventrally flattened by laterally compressed; compare a crab with a shrimp for a crustacean equivalent). It had a huge head and it had sort of a more greyhound like posture (as early crocs did, they only went low and more sprawled later on). So think of a huge head of teeth that can run faster than you and is 15-20 foot long and it is chasing you to make you its next meal.